Introduction

KernJC (Kernel JiaoChang /dʒaʊ tʃɑ:ŋ/) is a vulnerability reproduction tool for Linux kernel. The goal of KernJC is to construct reproducible environments for Linux kernel vulnerabilities, where the real vulnerable kernel version is compiled with the correct kernel configs to make the vulnerability available and triggerable.

Main Features:

1. Auto-detect and avoid spurious vulnerable version claims from online databases (e.g., NVD).
2. Auto-resolve vulnerability related kernel config dependencies.
3. Docker-like interface for vulnerability reproduction process management.
4. Incremental update of local knowledge base (Information of vulnerabilities and patches).

Workflow

The workflow of KernJC is shown as below:

You can refer to KernJC paper for more details.

Installation

KernJC is designed to run on Linux hosts with Intel/AMD CPUs. Currently only Ubuntu distributions are tested. The KernJC itself does not require distribution specific features (e.g., package management), but the tools/create-image.sh script (from syzkaller project) to build the base root filesystem image is distribution specific. If you are using other distributions, you may need to modify the script to make it work.

Install system-level dependencies:

sudo apt-get install -y git build-essential libssl-dev libncurses5-dev flex bison libelf-dev qemu-system qemu-utils gcc g++ make python3 python3-pip debootstrap gcc-multilib bc
pip3 install virtualenv

Clone the repository and install dependencies:

# Python >= 3.9 is required
git clone https://github.com/NUS-Curiosity/KernJC
cd KernJC
virtualenv -p /usr/bin/python3 venv
source venv/bin/activate
pip install -r requirements.txt

Then run the following command for initialization:

cp config.yaml.tmpl config.yaml
# run kjc to initialize dirs
./kjc update
# build base root filesystem image
cd tools/
./create-image.sh

Note that you need to input your own NVD API key in config.yaml to enable database updating. If you do not have an NVD API key, you can apply for one here.

Quick Start

Build a vulnerable environment for CVE-2016-10150:

$ ./kjc build CVE-2016-10150
[*] Removing potential FP versions for CVE-2016-10150
[+] Auto-selected kernel version: 4.8.12
[*] Initializing env
[*] Downloading 4.8.12 kernel source code
    100%|████████████████████████████████████████████134/134
[*] Decompressing kernel source code
[*] Building kernel source code
[*] Applying custom config
[*] Loading default custom config
[*] Generating potential configs based on kcfg graph
[*] Finding kernel configs for CVE-2016-10150 in env a30ebfa6f5747fa9
[*] Building kcfg graph for env a30ebfa6f5747fa9
[+] Built kcfg graph (12050 nodes, 21525 edges)
[+] Found 37 potential configs based on kcfg graph
[*] Loading CVE-2016-10150 related custom config
[!] Vuln config file not found. Using default config.
[*] Merging custom config with .config
[+] Applied custom config
... kernel compilation output omitted ...
[+] Built kernel source code
[*] Preparing rootfs (overlay image)
[+] Env a30ebfa6f5747fa9 created

List and inspect the built environment:

$ ./kjc ps -a
+------------------+----------------+--------+---------+
| ID               | CVE            | Kernel | Status  |
+------------------+----------------+--------+---------+
| a30ebfa6f5747fa9 | CVE-2016-10150 | 4.8.12 | stopped |
+------------------+----------------+--------+---------+
$ ./kjc info a3
{'create_time': 1699779548.215992,
 'cve': 'CVE-2016-10150',
 'ip': None,
 'kernel_version': '4.8.12',
 'pid': None,
 'port': None,
 'status': 'stopped'}

Start the environment:

$ ./kjc start --enable-kvm a3
[*] Starting env a3
[+] Started env a30ebfa6f5747fa9 (QEMU pid: 60566)

Compile the PoC and copy it to the environment:

$ cd db/pocs/cve-2016-10150/; gcc -o poc poc.c -static; cd -
~/pjts/KernJC
$ ./kjc cp db/pocs/cve-2016-10150/poc a3:/home/user/
Warning: Permanently added '[localhost]:10000' (ECDSA) to the list of known hosts.
poc

Open a new terminal and monitor the kernel logs:

$ ./kjc logs -f a3
[  OK  ] Reached target Graphical Interface.
         Starting Update UTMP about System Runlevel Changes...
[  OK  ] Finished Update UTMP about System Runlevel Changes.

Debian GNU/Linux 11 kernjc ttyS0
... output omitted ...

Add user user into kvm group (only for CVE-2016-10150):

$ ./kjc attach a3
... output omitted ...
user@kernjc:~$ su # password: neo
Password:
root@kernjc:/home/user# /usr/sbin/adduser user kvm
Adding user `user' to group `kvm' ...
Adding user user to group kvm
Done.

Run the PoC in the environment:

$ ./kjc exec a3 /home/user/poc
Warning: Permanently added '[localhost]:10000' (ECDSA) to the list of known hosts.

In the kernel logs terminal, we can see the KASAN report:

$ ./kjc logs -f a3
... output omitted ...
[  408.497181] ==================================================================
[  408.498170] BUG: KASAN: use-after-free in kvm_vm_ioctl+0x1150/0x1340 at addr ffff88006b8c9a40
[  408.498170] Read of size 8 by task poc/2983
[  408.498170] CPU: 1 PID: 2983 Comm: poc Tainted: G    B           4.8.12 #1
[  408.498170] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
[  408.498170]  0000000000000097 ffff88006118faf0 ffffffff81bfe5a2 ffff88006cc018c0
[  408.498170]  ffff88006b8c9a20 ffff88006b8c9a60 ffffffff83a46400 ffff88006118fb18
[  408.498170]  ffffffff815c8cbc ffff88006118fba8 ffff88006b8c9a20 ffff88006cc018c0
[  408.498170] Call Trace:
... output omitted ...

Stop and remove the environment:

$ ./kjc rm --force a3
[+] Env a30ebfa6f5747fa9 removed

Note:

1. You can ./kjc attach ENV_ID and run the PoC in the shell.
2. You can ./kjc rm --force ENV_ID to remove the environment without stopping it.
3. PoCs in db/pocs/ are collected from the Internet. Welcome to contribute more PoCs.
4. In the vuln env, you can su root with password neo to do privileged operations if needed.
5. Ensure that your local compilation toolchain is compatible with the target kernel version and PoC code. If not, the build process may fail.
   • It is recommended to setup KernJC in old Ubuntu containers when reproducing old vulnerabilities.

Usage

You can run ./kjc -h to see the usage of KernJC:

$ ./kjc -h
usage: kjc [-h] [-v] {update,build,start,stop,attach,exec,cp,logs,rm,ps,enter,info,query} ...

KernJC - A Linux kernel vulnerability reproduction tool

optional arguments:
  -h, --help            show this help message and exit
  -v, --version         show program's version number and exit

subcommands:
  {update,build,start,stop,attach,exec,cp,logs,rm,ps,enter,info,query}
    update              update local knowledge base
    build               build a vuln env
    start               start a vuln env
    stop                stop a vuln env
    attach              attach to a vuln env
    exec                execute a command in a vuln env
    cp                  copy files between host and a vuln env (ENV_ID:/path/to/file)
    logs                show QEMU logs of a vuln env
    rm                  remove a vuln env
    ps                  list vuln envs
    enter               enter an env dir on host
    info                show info of a vuln env
    query               query a vulnerability

Citation

If you use KernJC, please cite the following paper:

@inproceedings{ruan2024kernjc,
  author = {Ruan, Bonan and Liu, Jiahao and Zhang, Chuqi and Liang, Zhenkai},
  title = {KernJC: Automated Vulnerable Environment Generation for Linux Kernel Vulnerabilities},
  year = {2024},
  isbn = {9798400709593},
  publisher = {Association for Computing Machinery},
  address = {New York, NY, USA},
  url = {https://doi.org/10.1145/3678890.3678891},
  doi = {10.1145/3678890.3678891},
  booktitle = {Proceedings of the 27th International Symposium on Research in Attacks, Intrusions and Defenses},
  pages = {384–402},
  numpages = {19},
  keywords = {Linux Kernel, Reproduction, Vulnerable Environment},
  location = {Padua, Italy},
  series = {RAID '24}
}